1. Field of the Invention
The invention generally relates to electronic devices. More particularly, the invention relates to a communications device and a transmitter included therein.
2. Background
There is an ever present need to reduce the power consumption of electronic devices. For example, a laptop computer or a wireless phone typically includes a battery to store and provide electrical energy for the operation of the electronic device. A user can operate the electronic device through the battery when no other source of electrical energy is available, or when the user wants to be mobile. Batteries, however, store only a limited amount of electrical energy, which is consumed by the electronic device.
The batteries, thus, have to be recharged after the electronic device has been used for a certain time. The time interval between two subsequent charging events is expressed as operating time. In wireless phones, for example, the operating time can further be divided into a stand-by time and a talk time.
The user of a wireless communications device such as a mobile unit or a cellular phone typically desires to have an operating time, particularly a talk time, which is as long as possible. Additionally, the user generally expects the wireless device to be as small and as light as possible. Because the operating time is dependent from the capacity and, thus, usually from the size of the battery, small size, low weight, long operating time of the wireless, device are often contradictory expectations.
To fulfill these expectations, manufacturers seek to increase the capacity of the batteries without increasing the size and weight of the batteries. In addition, manufacturers of wireless devices have developed wireless devices which operate at lower voltages, for example 3.3 volts, to increase the stand-by time and the talk time.
In one embodiment, a communications device uses an amplifier module to transmit signals. The amplifier module is configured to amplify a signal. The amplifier module includes an amplifier circuit and a control module. The control module is configured to vary the operating parameters of the amplifier circuit based on a desired output power level. The control module relies on stored data values to dynamically vary the operating parameters of the amplifier circuit so as to increase the efficiency of the amplifier circuit.
The transmit power of a communication device, typically varies depending on the transmit conditions, the proximity of the communications device to a base station, etc. For example, a communications device may transmit at maximum power when poor transmit conditions exist. In many devices, the output power amplifier is optimized to generate the maximum power output.
If the transmit conditions are favorable or if a communications device is near a base station, the communications device often transmits at less than the maximum output power. Statistically speaking, a communications device typically spends most of its operational life transmitting at less than maximum power. For example, in a code division multiple access (CDMA) cellular phone, most of the time the phone operates below the maximum power output level within a range from about xe2x88x925 dBm (measured decibels referenced to a power of 1 milliwatt) to about +8 dBm. Accordingly, one embodiment of the invention increases the output power efficiency when an electronic devices operates at a lower output power level.
In another embodiment of the invention, a wireless communications device has an amplifier module which is configured to amplify a radio frequency (RF) signal with increased efficiency. The amplifier module comprising an input terminal which receives a control signal comprising a plurality of pulses, wherein the number of pulses within a predetermined time period identify a desired power level.
The amplifier module further comprising a control circuit in communication with the control signal. The control circuit comprising at least one counter which counts the number of pulses occurring within the predetermined time period so as to generate a control value.
The amplifier module further comprising a first memory array in communication with the control value. The first memory array comprising multiple entries, each entry comprising a power value, wherein the first memory outputs the power value which corresponds to the control value. The amplifier module further comprising a second memory array in communication with the control value. The second memory array comprising multiple entries, each entry comprising a bias value, wherein the second memory outputs the bias value which corresponds to the control value.
The amplifier module further comprising an amplifier circuit which is in communication with the power value, the bias value and a radio frequency (RF) signal. The amplifier circuit is configured to vary the amplification of the radio frequency signal based on the power and bias values, wherein the power and bias values increase the efficiency of the amplifier circuit at the desired power level.
In another embodiment, the power values determine the amount of power voltage applied to the amplifier circuit. In yet another embodiment, the bias values determine the amount of bias voltage applied to the amplifier circuit. In an additional embodiment, the first and second memory arrays are located in a single memory array.
In one embodiment, the power value is a digital power value. In another embodiment, the communications device further comprises a digital-to-analog converter which converts the digital power value to an analog power value. In yet another embodiment, the bias value is a digital bias value. In an additional embodiment, the communications device further comprises a digital-to-analog converter which converts the digital bias value to an analog bias value.
In one embodiment, the radio frequency signal is a Global System for Mobile Communications (GSM) communications signal. In another embodiment, the radio frequency signal is a Personal Communications System (PCS) communications signal. In yet another embodiment, the radio frequency signal is an Advanced Mobile Phone Systems (AMPS) communications signal.
In one embodiment, the radio frequency signal is compatible with the code division multiple access (CDMA) standard. In another embodiment, the radio frequency signal is compatible with the frequency division multiple access (FDMA) standard. In yet another embodiment, the radio frequency signal is compatible with the time division multiple access (TDMA) standard.
One embodiment of the invention relates to an amplifier control circuit comprising an input which receives a first signal indicative of a desired power level. The amplifier control circuit further comprising a memory. The memory comprising a plurality of data values wherein the data values represent amplifier operational parameters.
The amplifier control circuit further comprising a control circuit in communication with the input and the memory. The control circuit configured to access at least one of the data values in the memory in response to the first signal. The control circuit further configured to generate a second signal based on the selected data value.
In one embodiment, the first signal includes pulses of varying duration which are indicative of the desired power level. In another embodiment, the control circuit includes a counter which counts the pulses to generate a value representing the counted pulses within a predetermined period of time. The value being indicative of the desired power level.
In one embodiment, the data values represent values for powering an amplifier circuit. In another embodiment, the data values represent values for biasing an amplifier circuit. In yet another embodiment, the first signal is a digital signal. In an additional embodiment, the first signal transmits a digital value. In another embodiment, the data values represent values for biasing an amplifier circuit.
One embodiment of the invention relates to an amplifier control circuit comprising a first means for storing a plurality of data values wherein the data values represent amplifier operational parameters. The amplifier control circuit further comprising a second means in communication with a first signal that indicates a desired power level. The second means using the first signal to address at least one of the data values in the first means. The second means also generating a second signal based on the addressed data value.
One embodiment of the invention relates to a method for increasing the power efficiency of an amplifier module. The method comprising the act of receiving a first control signal indicative of a power level output of the amplifier module. The method further comprising the act of using the control signal to address memory locations, each memory location storing at least one operating characteristic of the amplifier module. The method further comprising the act of reading from the addressed storage locations to generate at least a second control signal, the second control signal configured to increase the power efficiency of the amplifier module.
In one embodiment, the control signal is a pulse duration modulation signal. In another embodiment, the method further comprising the act of counting the pulses of the control signal within a predetermined period of time to generate a digital value representing the power level. In yet another embodiment, the method further comprising the act of using the digital value to address the storage locations.